A car navigation system is a navigation system designed for a use on a vehicle, and provides a function of guiding a current position based on a map, or searching and guiding a route from a starting point to a destination. Recently, the car navigation system provides a function of guiding an optimal route to a user by reflecting real-time traffic information due to recent development of communication technology.
In such a vehicle navigation system, a global positioning system (GPS) may be given as a typical method for identifying a position of the vehicle.
The GPS determines a position of a satellite and a receiver by receiving signals transmitted from three or more GPS satellites, and may obtain a distance between the satellite and the GPS receiver by measuring a time difference between a signal transmitted from the satellite and a signal received by the GPS receiver. In addition, since the transmitted signal may include information related to the position of the satellite, the position of the reception may be calculated by using a triangulation method when the distance to at least three satellites and the position of each satellite are known.
However, the position calculated based on the GPS signal may include many errors due to many environmental factors. In particular, in an area having high density of high-rise buildings, in which irregular reflection occurs or in a shadow area, the GPS reception signal may include errors, and accordingly, the position calculated from the GPS signal may be different from the actual position.
The vehicle navigation system may guide a path to a destination by matching a pre-set path to the location of the vehicle, and perform a re-search of the path, when the vehicle deviates the pre-set path. When an error occurs in the position value calculated based on the GPS signal, even if the actual vehicle is located on the pre-set path, the vehicle navigation system may determine a deviation of the path due to the error of position measurement. Thus, the vehicle navigation system may perform an unnecessary re-search, which causes inconvenience to the user.